1. Technical Field
The present invention relates to an improved data processing system and in particular to a method and apparatus for servicing exceptions occurring in a data processing system. Still more particularly, the present invention provides a method and apparatus for servicing just in time compiler generated errors.
2. Description of Related Art
Java is an object oriented programming language and environment focusing on defining data as objects and the methods that may be applied to those objects. Java is designed to solve a number of problems in modern programming practice. Java is able to support applications for many types of data processing systems, which may contain a variety of central processing units and operating systems architectures. To enable a Java application to execute on different types of data processing systems, a compiler typically generates an architecture-neutral file format--the compiled code is executable on many processors, given the presence of the Java run time system. The Java compiler generates bytecode instructions that are non-specific to a particular computer architecture. A bytecode is a machine independent code generated by the Java compiler and executed by a Java interpreter. A Java interpreter is a module that alternately decodes and executes a bytecode. The decoding of the bytecode places the instruction into an executable form for the computer on which the code is to be executed. Then, the instruction is executed by the computer. These bytecode instructions are designed to be easy to interpret on any machine and easily translated on the fly into native machine code.
The Java virtual machine (JVM) is a virtual computer component that resides only in memory. A JVM includes components necessary to run a program on a computer, including an interpreter. The JVM allows Java programs to be executed on different platforms as opposed to only the one platform for which the code was compiled. Java programs are compiled for the JVM. In this manner, Java is able to support applications for many types of data processing systems, which may contain a variety of central processing units and operating systems architectures. To enable a Java application to execute on different types of data processing systems, a compiler typically generates an architecture-neutral file format--the compiled code is executable on many processors, given the presence of the Java run time system. The Java compiler generates bytecode instructions that are non-specific to a particular computer architecture. A bytecode is a machine independent code generated by the Java compiler and executed by a Java interpreter.
When extra speed in executing a Java program or applet is needed, a just in time (JIT) compiler may be used to translate bytecodes for a method or class into native machine instructions before executing them. Typically, this compilation only occurs once per method. Some JIT compilers may compile entire classes, rather than one method at a time.
In some situations, a JIT compiler may produce invalid results when compiling bytecodes from a given method of a class into instructions or machine code for execution on the computer. These errors do not occur if the code is not just in time compiled. Typically, these errors in execution of native instructions occur as a result of faulty logic in the JIT compiler. Traditionally, this type of error may be addressed by changing the bytecodes to avoid the problem. In many cases, such a fix is not possible or reasonable. Another approach to this problem is to make changes to the JIT compiler itself. Typically, such changes may be slow or infrequent. A third alternative is to disable the JIT compiler, which may result in performance costs for methods that would be JITed and not cause errors or exceptions. Currently, a mechanism for avoiding these errors is unavailable.
Therefore, it would be advantageous to have an improved method and apparatus for servicing errors or exceptions generated by a JIT compiler.